Unstabilised Phosphonium Ylid Formation Wittig Reaction

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The unstabilised phosphonium ylids are formed from the reaction of a phosphine usually triphenylphosphine with an alkyl halide e.g. ethyl bromide to give a phosphonium salt. This is then deprotonated using a strong base (NaH in this example but usually BuLi) to give the unstabilised ylid which can undergo a Z-selective Wittig reaction.

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R. Robiette, J. Richardson, V. K. Aggarwal and J. N. Harvey, J. Am. Chem. Soc., 2006, 128, 2394–2409.